Enzyme immunoassay (EIA) methods have been described, Guesdon J., Ternynck, T., Avrameas, S., "The Use of Avidin-Biotin Interaction in Immunoenzymatic Techniques," J. Histochem Cytochem 27:1131-1139, 1979. Guesdon et al tested the effects of labeling antibodies, antigens and enzymes with biotin in EIA procedures. The biotin-avidin interaction is well-known and has been studied rather exhaustively, and has been used in purification of reagents by coupling avidin to a Sepharose chromatographic column, conjugating biotin to a protein to be purified, binding the biotinylated protein to the column, washing the column, and then eluting the purified protein-biotin conjugate protein from the column. Liu, F., Zinnecker, M. Hamaoka, T. and Katz, D. H., J. Biochemistry 18:690, 1979.
The measurement of HCG in serum or urine is of interest in the diagnosis of early pregnancy, detection of ectopic pregnancies, and in monitoring various tumors. Walsh, P. R., Wang M., Gittermann, M. L., CLINICAL IMMUNOCHEMISTRY, American Association for Clinical Chemistry, 1978, Natelson, S. et al, Eds., pp. 306-328.
The use of filter papers, usually in the form of small discs, in various assay procedures is well-known. However, efforts to develop an assay method for HCG using filter paper discs has not been successful. After considerable work, it was discovered that the methods based upon binding HCG antibody to a disc and reacting the disc with a solution suspected of containing HCG, e.g., urine, were of poor reliability and sensitivity. Moreover, discs and filter paper devices cannot be manufactured by known techniques in a satisfactory manner. The present invention overcomes these disadvantages and makes possible a rapid, reliable and simple enzyme immunoassay for HCG in urine, or other solution.